This invention relates generally to hydraulic valves, and more particularly to fuel injectors having spill valves with hydraulically assisted opening.
In many fuel injectors which utilize a spill valve to relieve fluid pressure in the fuel pressurization chamber, a swift opening of the spill valve is desirable. This is beneficial because the longer the spill valve remains in the closed position after an injection event, the longer various components, such as cam and rocker arm assemblies, spend pressurizing fuel as opposed to merely displacing it. In order to prevent excess consumption of engine energy by unnecessarily pressurizing fuel after injection has ended, engineers are always searching for a means to more quickly open the spill valve. A number of fuel injectors currently employ a spill valve to relieve pressure within the fuel pressurization chamber. In these previous fuel injectors, the spill valve must be capable of opening against the action of the hydraulic forces present in the fuel injector which tend to slow this movement to the open position. In these previous injectors, the spill valve spring preload was often low, which is generally not beneficial for spill valve opening. While these foregoing fuel injectors have performed impressively, there is room for improving the speed with which the spill valve opens.
The present invention is directed to overcoming one or more of the problems described above and to exploiting hydraulic forces for a more abrupt opening of the spill valve.
A hydraulic valve with hydraulically assisted opening comprises a valve body that defines a fluid passage which includes an upstream segment and a downstream segment. Contained within the valve body is a moveable valve member which includes a hydraulic surface. The hydraulic surface is exposed to fluid pressure within the downstream segment of the fluid passage. When the valve member is in a closed position, the upstream segment of the fluid passage is closed to the downstream segment. The upstream segment is fluidly connected to the downstream segment when the valve member is away from the closed position.